Automatic apparatus for controlling the childbirth labour

ABSTRACT

Apparatus for controlling the childbirth labour comprising: an electromyographic unit ( 4 ) with sensors ( 3 ) associated therewith for detecting the electrical signals of a parturient&#39;s uterus and means ( 6 ) for analysing and processing said electrical signals, and a pneumatic belt ( 1 ) to be fixed around the parturient&#39;s abdomen and having sensors ( 15 ) associated therewith to detect the variation of the internal pressure due to uterine contractions, and means ( 2 ) for inflating said belt to provide a thrust as an aid for the expulsion of the fetus, characterized in that a device ( 7 ) is provided, associated with said sensors ( 15 ) and ( 3 ), to control the activation of said means ( 2 ) for the inflation of the pneumatic belt ( 1 ).

The present invention refers to an automatic apparatus for controllingthe childbirth labour.

It is known that the term “childbirth labour” refers to the complex ofmechanical and dynamic phenomena which lead to the expulsion of thefetus and placenta and which, conventionally, is subdivided into threestages:

-   -   the first stage, which relates to the dilatant period, that is,        to the beginning of the labour up to the complete dilatation of        the uterine cervix, is in turn subdivided into a “latent        period”, characterized by a dilatation of 3-4 cm, and a        following “active period” which leads to a complete dilatation;    -   the second stage, which relates to the expulsive period, goes        from the complete dilatation to the delivery;    -   the third stage, which relates to the discharge of the        after-birth, ends up with the expulsion of the placenta.

It is also known that the deficiency, alteration or insufficientcoordination of the uterine contractions may cause problems upon theexpulsive stage, which is the delivery's most delicate one. Inparticular, it may happen that the uterus is not able to produce, withits contractions, a force of an intensity sufficient to conclude thedelivery's expulsive stage (hypokinesia). It may happen, besides, thatthe expectant mother, in spite of the therapies commonly provided fortreating such cases, is unable to produce a thrust—through acorresponding contraction of the abdominal press—adding up to the forcegenerated by the uterine contraction. And, since a prolonged rest of thefetus in the delivery duct may seriously endanger the health conditionthereof, a so-called Kristeller manoeuvre is generally performed by thehealth personnel, which consists in exerting, with an arm, a series ofthrusts upon the bottom of the uterus, with the purpose of assisting thenatural expulsive forces and speeding up the progression anddisengagement of the fetus. However, this manoeuvre has risks inasmuchas it may cause the rupture of the uterus, the detachment of theplacenta and acute fetal pains as well.

Also known in obstetrics is the use of the electromyograph (EMG) bywhich it is possible to register the electrical phenomena of the uterus'natural and involuntary contractions by deriving the relevant electricalpotentials via electrodes applied on the patient's abdomen: anapplication software to be run on a PC provides for a graph of saidelectrical potentials versus time. However, the use of only an EMG doesnot provide any aid to the parturient's thrust and, moreover, thecontraction graphs plot also other spurious signals such as spikes,tensions induced by the activation of other apparatuses and by neon glowlamps.

Also known in obstetrics is the use of the Pressure Labor Assister(PLA), with pressure sensors-controlled software, which utilizes thepressure increase inside an air chamber—formed within an abdominal bandfixed around the patient's body—and which occurs as a consequence of thenatural uterine contractions, to provide an automatic extra force, as anaid to the parturient, for the expulsion of the future baby.

On the other hand, this known device PLA does not provide a chart nor arecord of the uterine contractions, and may also be a source of dangers,inasmuch as the possible overpressures on the pneumatic band, which areindependent of the contractions but are due instead, for example, tomore or less involuntary movements of the parturient, are alwaysinterpreted as a signal of uterine contraction and, in such case, it mayoccur that the consequent inflation of the abdominal pneumatic band willtake place during a rest period, between one contraction and another,thereby dangerously reducing the inflow of blood to both the parturientand future baby.

One object of the present invention is to overcome the drawbacks of thecommon and widespread Kristeller technique.

A further object of the present invention is to enable, in case ofascertained insufficient expulsive force of the uterine naturalcontractions, the person in charge of the childbirth to activate adevice providing an extra thrust for the expulsion of the fetus—theactivation of said device depending, for a higher safety measure, on theuterine contraction and not on false signals.

This result has been achieved, according to the invention, by adoptingthe idea of making an apparatus having the characteristics disclosed inthe independent claims. Further characteristics being set forth in thedependent claims.

The advantages deriving from the present invention lie essentially inthe fact that it is possible to automatically ensure, whenever the needarises and in a non-invasive fashion, the highest accurate coordinationbetween the internal thrust produced by both natural and involuntaryuterine contractions and the supplementary thrust produced by means of apneumatic belt intended to act on the parturient's abdomen; that anapparatus according to the invention is safe, utilizable with relativesimplicity by the personnel assisting the expectant mothers, relativelysimple to make and reliable also after a prolonged service period. Allthis by making use of an integrated system allowing the auxiliarypneumatic thrust to be obtained only when the parturient hascontractions detected simultaneously and safely by both pneumatic andelectrical signals independent from each other and deriving from saidcontractions.

These and other advantages and characteristics of the invention will bebest understood by anyone skilled in the art from a reading of thefollowing description in conjunction with the attached drawings given asa practical exemplification of the invention, but not to be consideredin a limitative sense, wherein:

FIG. 1 is a simplified block diagram of an apparatus according to theinvention, showing a possible configuration thereof upon use;

FIG. 2 is a schematic plan view of the pneumatic belt (1) shown in theschematic diagram of FIG. 1;

FIG. 3 is a further simplified block diagram of an apparatus accordingto the invention.

Reduced to its basic structure, and reference being made to the figuresof the attached drawings, an apparatus for controlling the childbirthlabour, according to the invention, comprises:

-   -   means for detecting the electrical activity of the uterus,        comprising two or more outer electromiographic sensors (3) (that        is, sensors of non-invasive type) able to be positioned on the        skin of the parturient's abdomen at two regions corresponding to        preset points of the uterus U;    -   means for registering and plotting the electrical signals of the        uterine contractions thus detected;    -   means (4, 5) for analysing said electrical signals in relation        to a predetermined scheme of analysis;    -   an inflatable belt (1) associated with pneumatic means (2) able        to inflate it under control and at preset pressure, and        respectively deflate it: the said belt (1) being put on by the        expectant mother in such a way that a surface (10) of the same        belt will act, when inflated, upon the bottom of the uterus;    -   means (7) to control the activation and deactivation of said        pneumatic means (2) in response to the pressure variation due to        the contraction and sensed by the pneumatic belt, and to the        result of analysis of the uterus' electrical activity.

In particular, the said analysis means comprise an electromyographicapparatus (4), associated with said sensors (3) via an interface (5)allowing the amplification and pre-processing of the signals andprovided with a section (6) for processing the signals detected by thesensors (3) and transmitted through the interface (5) with theirrespective time value, as best described later on in greater details.

In case of two-channel electromyographic apparatuses, such as the TECASinergy Multimedia of the Oxford Instruments, two channel sensors orelectrodes and one ground electrode are used: the channel sensors arepositioned simmetrically and horizontally in a skin region of theparturient's abdomen at about 5-15 cm of the umbilical transverse, andthe ground electrode is located on the internal side of the left thigh.

As for the said inflatable belt (1), this is of a type comprising an airchamber (11) with a coupling (12) for a tube (13) connectable to saidmeans (2), and provided with two wings (14) of a length sufficient forbeing tied up around the parturient's thorax: the said wings (14) beingable to be linked one to the other by “velcro”-type means 140 after thebelt has put on. Moreover, the pneumatic means (2) is internallyprovided with sensors (15) able to detect the pressure variations insidethe air chamber (11), which are due to the thrusts exerted by theparturient's abdomen as a consequence of the uterine contractions, thatis, relative to a basic pressure value corresponding to the initialinflation (for example, when using a belt of MITECH-200-A type, a basicvalue of 8-16 kPa). The belt in question is intended to exert, as bestdescribed later on, a predetermined pressure P uniformly distributed onthe uterus' bottom.

Provided upstream of said pneumatic means (2) is an activation device(7) which, in turn, is associated with sensors (15) located within themeans (2), and with the electromyographic apparatus (4): said device (7)determining the activation of the pneumatic means (2), that is, theinflation of the belt (1), whenever both the uterine contraction signalson output from the sensors (15) and the signals on output from theapparatus (4) are present therein at the same time.

To be more precise, if, during the labour, the device (7) receivessimultaneously both the electrical signals from the means (4)—resultingof such intensity and shape as to correspond to those of the uterinecontractions (for example, electrical signals three times higher thanthe signals sensed between one contraction and another)—and thepneumatic signals detected by the sensors (15) and identified ascontraction signals as well, then, only in this case the said device (7)gives the command for the activation of the means (2), that is, for theinflation of the belt (1) at a pressure to be either preset or timelyestablished by the person in charge of the childbirth.

In other words, the activation of belt (1) and, accordingly, theauxiliary thrust P exerted by the latter on the parturient's abdomen incorrespondence of the uterus' bottom, takes place solely when there isoccur, simultaneously, on the one hand, an overpressure in the chamber(11) of belt (1) due to a deformation imposed by the abdominal muscleson the belt's wall because of a contraction and, on the other hand, thatis, in correspondence of sensors (3), a myoelectrical activity of presetintensity and in any case exceeding the intensity being present when nocontractions occur. The two detections are independent from each other,as being obtained from independent detection means, but are both relatedto a same event, that is, to the natural and involuntary uterinecontraction upon the active stage of the childbirth. It thus followsthat the actuation of the belt (1) results precisely in phase with theuterine contractions of greater intensity, as it is operated on thebasis of detections made both within the chamber (11) of belt (1) and onthe basis of detections made on the muscular electrical activity in themore directly involved abdominal region.

The time for the activation of belt (1), that is, the time ofoverpressure persistence within the chamber (11) of the same belt undercontrol of means (2), is adjustable by the health operator who assiststhe expectant mother and whose decisions are taken according to thetrend of the electromyographic contraction signals previously registeredfor the same patient.

As above described, the device (7) which controls the activation of themeans (2) provided for the inflation of the belt (1) is commonlyassociated with the pressure sensors (15) and with the electricalsensors (3) as well. However, the operator may cut off one or the otherconnection, owing to a malfunction of one of them or when he/she deemssuited to do so.

For example, it is possible to exclude the connection with the pressuresensors (15) so that the activation of the pneumatic means (2) becontrolled solely by electrical signals transmitted by the sensors (3);otherwise, it is possible to cut off the sensors (3), so that theactivation of the pneumatic means (2) be controlled solely by pressuresignals transmitted by the sensors (15). All this makes it possible touse the device in question also in case of malfunctions affecting eitherthe detection of pressure signals through the sensors (15) or thedetection of signals transmitted by the sensors (3), and to process thesignals by means of the electromyographic apparatus (4, 6).

In any case, the operator has faculty of excluding the automaticintervention of the system in order to use the latter only when the needarises.

With reference to the diagram of FIG. 3, the said device (7) comprisesan AND gate (70) whose inputs are connected, respectively, to the outputof the apparatus (4) and to the output of an A/D converter (150)provided downstream of sensors (15) housed in the belt (1). The outputof said AND gate is connected with the input of a D/A converter (72)which, on output, is connected with the means (2) which activate theinflation of the belt (1). Inserted on the line connecting the gate (70)with the converter (72) is a normally closed switch (71). Inserted onthe line connecting the converter (150) with the converter (72) is anormally opened switch (73). When the sensors (15) sense an overpressurein the chamber of belt (1), a corresponding electrical signal isproduced which, after being converted in digital form by the converter(150), is fed to the AND gate (70). Similarly, the signals on outputfrom the section (6) of the electromyiographic apparatus (4) come to theAND gate (70) which, when both signals are present, activates, throughthe converter (72), the opening of a solenoid of means (2) and,therefore, the inflation of the belt (1). The operator may decide to cutoff the AND gate (70), for example in case of ascertained failure of theapparatus (4), by merely opening the switch (71) and closing the switch(73). The switches (71) and (73) operate in push-pull mode.

The said data processing section (6) can advantageously consist of a PCassociated with the electromyiographic unit (4). Within the section (6),the signals coming from the sensors (3) and acquired by the system areprocessed according to a preset algorithm, for example, the onedescribed in the article “A fast algorithm for detecting contractions inuterine electromyography—a non invasive method utilizing higher-orderzero crossing for signal analysis” published in IEE Engineering andBiology—March/April 2000. Such an algorithm allows the obtainment of anestimator value to be compared with a predefined threshold. Throughoutthe time interval in which the estimator value exceeds said threshold,it is assumed that a contraction is taking place and a signal of logiclevel one is fed to the AND gate (70). Vice versa, when the estimatorvalue is below said threshold value, a signal of logic level zero is fedto the AND gate (70).

1. Apparatus for controlling the childbirth labour comprising: anelectromyographic unit with sensors associated therewith for detectingthe electrical signals of a parturient's uterus and means for analyzingand processing said electrical signals, and a pneumatic belt to be fixedaround the parturient's abdomen and having sensors associated therewithto detect the variation of the internal pressure due to uterinecontractions, and means for inflating said belt to provide a thrust asan aid for the expulsion of the fetus, characterized in that a device isprovided associated with said sensors and to control the activation ofsaid means for the inflation of the pneumatic belt.
 2. Apparatusaccording to claim 1, characterized in that the said device comprises anAND gate with its inputs being connected, respectively, to the output ofsaid electromyographic unit and to the output of an A/D converterlocated downstream of said sensors which are housed in the belt, andwith its output being connected with the input of a D/A converter whoseoutput is connected with said means for the inflation of the belt. 3.Apparatus according to claim 2, characterized in that a first switch isinserted on the line connecting the gate with the converter. 4.Apparatus according to claim 2, characterized in that a second switch isinserted on the line connecting the converter with the converter, saidsecond switch operating in push-pull mode with respect to said firstswitch.
 5. Apparatus according to claim 1, characterized in that thesaid means of the electromyographic unit consist of a PC associated withthe electromyographic unit.
 6. Apparatus according to claim 3,characterized in that a second switch is inserted on the line connectingthe converter with the converter, said second switch operating inpush-pull mode with respect to said first switch.